Solar energy is the most abundant energy resource on earth. Every year the world receives 30,000 times as much solar energy as is used by all humankind for light, heat, and transportation. But putting solar energy to work for you requires very specialized knowledge about yearly weather patterns, what solar technology is reliable and cost-effective, and what your energy use profile looks like. For twenty-five years, Solar Works has been helping clients answer these questions and design appropriate solar systems.
What are photovoltaics?
The term photovoltaic (PV) means to convert light directly into electricity though a photochemical reaction involving silicon, a semiconductor material ideal for this task due to its light sensitive properties. Photovoltaics are made of silicon, plus boron and phosphorous. In the presence of sunlight, an electric current is produced from the release of electrons contained in these three materials’ atoms. PV modules involve no moving parts and produce no pollution.
What is the difference between on-grid and off-grid PV systems?
Grid-connected PV systems operate in parallel with your local utility service, providing a supplemental source of clean, renewable energy. Direct current (DC) power from the solar modules is feed to an inverter that converts this energy to utility-grade alternating current (AC). This energy is then feed into a building’s load center, helping offset incoming utility power. These systems can be designed with storage batteries and a special “bi-modal” inverter to act as a back-up power source if utility power fails. Off-grid PV systems are designed as the primary power source for remote locations without utility service. These systems always have deep-cycle storage batteries and often are coupled with a fossil-fuel generator to provide reliable service regardless of weather conditions. These are called hybrid power systems.
How do grid-connect systems work?
There are two types of grid-tie systems, those with storage batteries and those without. Systems without batteries use PV modules connected directly to an inverter to create 120-volt utility-grade electricity. Power is produced during sunlight hours and is fed directly into a building’s electrical load center. This solar power supplements the utility power and reduces the amount of utility power used. If there is extra solar generation above what is needed in a house, it is sent back to the utility grid, spinning the customer’s meter backwards.
These systems are simple, reliable, and produce the most kilowatt-hours (kWh) per dollar invested. But there’s one thing they won’t do – keep the lights on during a power outage.
The second type of grid-tie PV system, those with batteries, overcome this limitation by use of a battery bank to store energy and a special “bi-modal” inverter. During a brownout or blackout, the inverter will disconnect from the utility and draw energy from the sn or battery bank to power house loads. The number of appliances that can be run, and the length of time they can run, depends on the size of the inverter and the battery bank.
Which system is right for me?
There are several key factors that must be considered when making this decision.
- Your current electrical consumption
- what % of your electric bill would you like the system to provide?
- Whether you want battery backup or not — if your primary concern is power outages, then you will need batteries.
- Your interest in being able to sell or “net meter” excess electricity back to your utility.
- How much non-shaded roof or ground area is available?
- Where does it make the most sense to locate the system?
- The amount you would like to invest in solar energy?
Solar Works staff members are available to help you answer these questions and choose the right system.
How does a solar hot water system work?
Modern solar water heating technology has been in use for over twenty-five years and is a proven, highly reliable technology with more than 100,000 installations in the United States.
In the Northeast, with its freezing climate, the most widely used system is called a closed-loop antifreeze system. Such a system has three major components: the collectors, a storage tank, and a heat exchanger. A non-toxic antifreeze solution (propylene glycol) is used to transfer heat from the collectors to the storage tank. All of our solar hot water systems are used as pre-heaters in conjunction with a conventional backup heating system. This means everyone can use solar hot water regardless of whether electricity, propane, oil, or another fuel is currently used.
Heating domestic hot water (DHW) is the second highest energy cost in a typical household. A family of four, using an electric hot water heater and paying $.12 per kilowatt-hour (kWh), will spend about $500 a year for hot water. A solar system can provide two-thirds or more of this energy at a cost equivalent to seven cents per kWh, a 40% savings.
Can I also heat my home with a solar thermal system?
Flat plate collectors can also be used to provide space heat in addition to domestic hot water. These systems typically have six to eight collectors rather than just two that are needed for domestic water heating. Homes that use radiant floor heating with underfloor tubing are ideally suited for active solar heating because radiant systems operate at a low temperature and the thermal mass of the floor can be used as a storage medium.
Can I heat my pool with solar collectors?
Absolutely! If you are currently using propane or oil to heat your pool, a solar pool heating system can pay for itself in a few years. Solar pool systems use low-cost plastic, unglazed collectors to effectively absorb solar energy during the spring, summer, and early fall. Pool water is circulated directly through the collectors, warming it with each pass.The operation of a pool system is simple and automatic. When the system controller senses that the collectors are warmer than the pool water, it opens a valve diverting water from the pool circulator through the collectors and then back into the pool. Our customers regularly report 80 degree pool temperatures by the end of May!
How can I incorporate energy efficiency along with my solar system?
Energy efficiency appliances can help you get the most out of your solar system. Investment in energy efficient lighting, heating equipment, refrigeration, and motors can provide a quick payback, increased comfort, and a reduced reliance on non-renewable energy sources. A Sunfrost refrigerator uses 1/4 the energy of the most best “energy star” conventional refrigerator on the market.